1. Field of the Invention
The present invention relates to a display control circuit which provides a window display in displaying means such as a liquid crystal display.
2. Description of the Prior Art
A liquid crystal display is largely used in an electronic device such as a small-sized computer or a word processor for Japanese and a window function is used in a display region of the liquid crystal display in order to increase display information. The window function is a function for displaying different display data in a specific display region (referred to as a window region hereinafter) set in the already displayed display screen. There are some cases where the window regions are set in a plurality of positions in the single display region and also there are some cases where another window region is superposed on the already displayed window display region.
In order to implement the above window function, it is necessary to delete an already displayed image in the window region when the window region is set and display the different display information in the window region. In this operation, a large amount of address operation is required. This address operation was performed by software operation through a CPU (central processing unit) comprised in the word processor for Japanese or the like in the prior art. This software operation requires high-speed operation of the CPU. Therefore, it is necessary to supply a relatively large power to the CPU. Although the high-speed address operation by the software is possible in the electronic device which is connected to a commercial ac supply, the high-speed operation of the CPU is difficult in the electronic device which is driven by a battery because a relatively small power is applied to the CPU in that device. Therefore, it is difficult to implement the window function.